Film bulk acoustic resonator having suppressed lateral mode

ABSTRACT

Film bulk acoustic resonator having suppressed lateral mode. In some embodiments, a film bulk acoustic resonator can include a piezoelectric layer having a first side and a second side, a first electrode having a first lateral shape implemented on the first side of the piezoelectric layer, and a second electrode having a second lateral shape implemented on the second side of the piezoelectric layer. The first and second lateral shapes can be selected and arranged to provide a resonator shape defined by an outline of an overlap of the first and second electrodes. The resonator shape can include N curved sections joined by N vertices of an N-sided polygon. The resonator shape can be configured to have no axis of symmetry.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application No.62/724,753 filed Aug. 30, 2018, entitled FILM BULK ACOUSTIC RESONATORHAVING SUPPRESSED LATERAL MODE, the disclosure of which is herebyexpressly incorporated by reference herein in its respective entirety.

BACKGROUND Field

The present disclosure relates to bulk acoustic resonators.

Description of the Related Art

A bulk acoustic resonator is a device having a piezoelectric materialbetween two electrodes. When an electromagnetic signal is applied to oneof the electrodes, an acoustic wave is generated in the piezoelectricmaterial and propagates to the other electrode.

Depending on the thickness of the piezoelectric material, resonance ofsuch an acoustic wave is established, and on the other electrode, anelectromagnetic signal having a frequency corresponding to the resonantacoustic wave is generated. Thus, such a bulk acoustic resonator can beutilized to provide filtering functionality for an electromagneticsignal such as a radio-frequency (RF) signal.

In many applications, the piezoelectric material between the electrodesis relatively thin and implemented as a film. Thus, a bulk acousticresonator is sometimes referred to as a thin-film bulk acousticresonator (TFBAR) or as a film bulk acoustic resonator (FBAR).

SUMMARY

According to a number of implementations, the present disclosure relatesto a bulk acoustic resonator that includes a piezoelectric layer havinga first side and a second side, a first electrode having a first lateralshape implemented on the first side of the piezoelectric layer, and asecond electrode having a second lateral shape implemented on the secondside of the piezoelectric layer. The first and second lateral shapes areselected and arranged to provide a resonator shape defined by an outlineof an overlap of the first and second electrodes. The resonator shapeincludes N curved sections joined by N vertices of an N-sided polygon.The resonator shape is configured to have no axis of symmetry.

In some embodiments, the quantity N can be an integer greater or equalto 4. In some embodiments, the quantity N can be equal to 5.

In some embodiments, each of the N curved sections can be a smoothcurve. Each of the N vertices can be defined by joining of twoneighboring smooth curves, such that the two neighboring smooth curvescombined is not a smooth curve due to the respective vertex. In someembodiments, each of the N vertices can be a sharp point between therespective neighboring smooth curves. In some embodiments, each smoothcurve can have an inward facing concave shape.

In some embodiments, each of the N curved sections can be a part of anellipse. In some embodiments, at least two of the N curved sections canbe parts of one ellipse. In some embodiments, the N curved sections canbe parts of N respective ellipses.

In some embodiments, the bulk acoustic resonator a film bulk acousticresonator.

In some embodiments, neither of the first and second lateral shape canhave the same lateral shape as the resonator shape. In some embodiments,at least one of the first and second lateral shape can be configured tohave substantially the same lateral shape as the resonator shape. Forexample, one of the first and second lateral shape can be configured tohave substantially the same lateral shape as the resonator shape, andthe other lateral shape can be configured to have a larger area tothereby include a non-overlapping portion. In another example, each ofthe first and second lateral shape can be configured to havesubstantially the same lateral shape as the resonator shape.

In some implementations, the present disclosure relates to a method forfabricating a bulk acoustic resonator. The method includes forming afirst electrode having a first lateral shape, providing a piezoelectriclayer on the first electrode, and forming a second electrode having asecond lateral shape on the piezoelectric layer such that thepiezoelectric layer is between the first and second electrodes. Theforming of the first electrode and the forming of the second electrodeinclude selecting and arranging the first and second lateral shapes toprovide a resonator shape defined by an outline of an overlap of thefirst and second electrodes, such that the resonator shape includes Ncurved sections joined by N vertices of an N-sided polygon, and suchthat the resonator shape is configured to have no axis of symmetry.

In a number of implementations, the present disclosure relates to a filmbulk acoustic resonator device that includes a substrate, first andsecond electrodes implemented over the substrate, and a piezoelectriclayer implemented between the first and second electrodes. The first andsecond electrodes are configured to provide a resonator shape defined byan outline of an overlap of the first and second electrodes, with theresonator shape including N curved sections joined by N vertices of anN-sided polygon, and the resonator shape being configured to have noaxis of symmetry.

In some embodiments, the film bulk acoustic resonator device can be aradio-frequency filter.

In accordance with some implementations, the present disclosure relatesto a packaged module that includes a packaging substrate configured toreceive a plurality of components, and a film bulk acoustic resonatordevice implemented on the packaging substrate. The film bulk acousticresonator device includes a substrate, and first and second electrodesimplemented over the substrate. The film bulk acoustic resonator devicefurther includes a piezoelectric layer implemented between the first andsecond electrodes that are configured to provide a resonator shapedefined by an outline of an overlap of the first and second electrodes,with the resonator shape including N curved sections joined by Nvertices of an N-sided polygon, and the resonator shape being configuredto have no axis of symmetry.

In some embodiments, the packaged module can be a front-end moduleconfigured to support wireless operations involving radio-frequencysignals.

In some implementations, the present disclosure relates to a wirelessdevice that includes an antenna configured to support either or both oftransmission and reception of respective signals, and a front-end systemin communication with the antenna. The front-end system includes a filmbulk acoustic resonator filter having a substrate, and first and secondelectrodes implemented over the substrate. The film bulk acousticresonator filter further includes a piezoelectric layer implementedbetween the first and second electrodes that are configured to provide aresonator shape defined by an outline of an overlap of the first andsecond electrodes, such that the resonator shape includes N curvedsections joined by N vertices of an N-sided polygon, and the resonatorshape is configured to have no axis of symmetry.

In some embodiments, the wireless device can be configured to providecellular communication functionality.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts a side view of a film bulk acoustic resonator (FBAR)device having a resonator formed on a substrate.

FIG. 1B shows a plan view of an outline of overlapping portions of thefirst and second electrodes.

FIG. 2A shows a resonator having a square shape, similar to the exampleof FIG. 1B.

FIG. 2B shows a resonator having a circular shape with a rotationalsymmetry about the center of the circle.

FIG. 3 shows an example of a non-circular elliptical shaped resonatorhaving a degree of symmetry that is lower than that of the circularshaped resonator of FIG. 2B.

FIG. 4 depicts a side view of an FBAR having a lateral shape that doesnot include an axis of symmetry.

FIGS. 5A-5E show an example of how a resonator can be designed toprovide the lateral shape of FIG. 4.

FIG. 6 shows plots of scattering parameter S21 for the square shapedresonator of FIG. 2A, the circle shaped resonator of FIG. 2B, and theellipse shaped resonator of FIG. 3.

FIG. 7 shows an enlarged view of a portion of FIG. 6, for the squareshaped resonator.

FIG. 8 shows an enlarged view of a portion of FIG. 6, for the circleshaped resonator.

FIG. 9 shows an enlarged view of a portion of FIG. 6, for the ellipseshaped resonator.

FIG. 10 shows an enlarge region similar to the examples of FIGS. 7-9,but for a resonator having an ellipse based shape with cuts.

FIGS. 11A and 11B show an example a resonator shape that includes acombination of two ellipse-based shapes.

FIGS. 12A and 12B show another example a resonator shape that includes acombination of two ellipse-based shapes.

FIGS. 13A-13D show that in some embodiments, a resonator shape caninclude a curved section for each side of a polygon.

FIG. 14 shows an example where a resonator shape has five curvedsections corresponding to a five-sided polygon.

FIG. 15 shows S21 plots for various shaped resonators.

FIG. 16 shows that in some embodiments, an FBAR device having one ormore features as described herein can be implemented as, or be a partof, a packaged filter.

FIG. 17 shows that in some embodiments, a radio-frequency (RF) modulecan include an FBAR device having one or more features as describedherein.

FIG. 18 depicts an example wireless device having one or moreadvantageous features described herein.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Described herein are various examples related to film bulk acousticresonators (FBARs) and related devices having suppressed or reducedlateral mode waves. Although such examples are described in the contextof FBARs, it will be understood that one or more features of the presentdisclosure can also be implemented in other types of resonators,including devices that are similar to FBARs but referred to in differentterms.

FIG. 1A depicts a side view of a typical FBAR device 10 having aresonator formed on a substrate 12. Such a resonator can be formed bypositioning a piezoelectric material layer 20 (also referred to hereinas a piezoelectric layer, or simply piezoelectric) between a firstelectrode (e.g., upper electrode 16) and a second electrode (e.g., lowerelectrode 14). FIG. 1B shows a plan view of an outline 21 of overlappingportions of the first and second electrodes. It will be understood thatthe piezoelectric material is present between the first and secondelectrodes 16, 14 and at least within such an outline. For the purposeof description, such an outline of overlapping portion of the electrodesand the piezoelectric layer can be referred to as a resonator shape orsimply as a resonator. In the example of FIG. 1A, such a resonator shape(21) is shown to be a square shape with a side dimension of A.

If a radio-frequency (RF) signal is applied to the resonator through oneof the electrodes, a corresponding acoustic wave is propagated throughthe piezoelectric layer 20 towards the other electrode and leaves thatelectrode as an RF signal having a frequency corresponding to a resonantfrequency of the acoustic wave established in the piezoelectric layer20. Thus, the resonator can provide an excellent filteringfunctionality, with the filtered frequency depending on the thickness ofthe piezoelectric layer.

Typically, much of the acoustic waves travel through the piezoelectriclayer 20 in a direction perpendicular to the upper and lower electrodes16, 20. For the purpose of description, such a propagation direction canbe assumed to be a Z-direction. In a typical FBAR device, thepiezoelectric layer 20 supports some lateral mode waves along one ormore directions (e.g., directions in X, Y or combination thereof).

It is noted that if a resonator has a symmetrical lateral shape, such asa square, a circle, etc., a portion of the lateral wave components maybe totally reflected and such total reflection may cause superpositionof the lateral waves, thereby generating undesired noise. Typically,such superposition of lateral waves caused by total reflection (orsubstantially total reflection) can result due to presence of opposingboundary surfaces that are parallel to each other. Such parallelsurfaces can include, for example, a surface defined by a plane, asurface defined by a point or small area of a tangent plane, or somecombination thereof.

For example, FIGS. 2A and 2B show resonators having relatively highdegrees of symmetry. More particularly, FIG. 2A shows a resonator 21having a square shape, similar to the example of FIG. 1B. Such a squareshape has an order of rotational symmetry (about the center of thesquare) of 4. FIG. 2B shows a resonator 21 having a circular shape; andsuch a circular shape has an order of rotational symmetry (about thecenter of the circle) of that is essentially infinite.

Referring to the example of FIG. 2A, the square shape of the resonator21 includes two sets of opposing side wall surfaces, with each sethaving opposing side wall surfaces that are parallel to each other.Accordingly, numerous lateral waves undergoing total reflections can besupported. For example, lateral waves undergoing total reflectionsbetween right and left side walls (when viewed as shown in FIG. 2A) aredepicted as double-ended arrows 22. Similarly, lateral waves undergoingtotal reflections between upper and lower side walls (when viewed asshown in FIG. 2A) are depicted as double-ended arrows 24.

Referring to the example of FIG. 2B, the circular shape of the resonator21 includes essentially an infinite number of pairs of tangent surfaces,with each pair of tangent surfaces being associated with tangent planeson the opposite sides of the circle. Accordingly, numerous lateral wavesundergoing total reflections can be supported. For example, lateralwaves undergoing total reflections between respective opposing tangentsurfaces and passing through the center of the circle are depicted asdouble-ended arrows 26.

FIG. 3 shows an example of an elliptical shaped resonator 21 having adegree of symmetry that is lower than that of the circular shapedresonator of FIG. 2B. Thus, such an elliptical shaped resonator includesless number of sets of opposing side wall surfaces. However, there aretangent surfaces associated with an ellipse that can be problematic interms of lateral waves. By way of an example, a pair of opposing tangentsurfaces at opposing ends of the major axis can support a lateral waveundergoing total reflections at the vertices. Similarly, a pair ofopposing tangent surfaces at opposing ends of the minor axis can alsosupport a lateral wave undergoing total reflections.

Referring to the example of FIG. 3, it is also noted that lateral wavesmay also be concentrated around either or both foci of the ellipticalshaped resonator 21. While such lateral waves, indicated as single-endedarrows 28, may not undergo total reflections between opposing surfaces,they still can be problematic.

In some embodiments, a resonator having one or more features asdescribed herein can include a lateral shape that does not include anaxis of symmetry, and/or does not include opposing parallel surfaces ortangent surfaces of the lateral boundary that are joinable by a normalline. FIG. 4 shows a FBAR device 100 having such a resonator.

Referring to FIG. 4, the FBAR device 100 can include a resonator 112formed on a substrate 102. Such a resonator can be formed by positioninga piezoelectric layer 110 between a first electrode (e.g., upperelectrode 106) and a second electrode (e.g., lower electrode 104). Forthe purpose of description, the resonator 112 can include overlappingportions of the first electrode 106, the piezoelectric layer 110, andthe second electrode 104. For the purpose of description, such anoverlapping portion of the electrodes and the piezoelectric layer can bereferred to as a resonator shape or simply as a resonator.

FIGS. 5A-5E show an example of how a resonator (112 in FIG. 5E) can bedesigned to provide some or all of the foregoing feature where thelateral shape of the resonator does not include an axis of symmetry,and/or does not include opposing parallel surfaces or tangent surfacesthe lateral boundary that are joinable by a normal line.

In some embodiments, such a resonator shape can be a part of anelliptical shape. For example, and as shown in FIG. 5A, an ellipticalshape 120 can be provided. To remove both of the symmetry axes (majoraxis and minor axis), such an elliptical shape can be cut along a line122 that forms a non-zero angle with respect to the minor axis. Asimilar cut can be made with respect to the major axis; however, in someembodiments, it is preferable to maintain a desired aspect ratio betweengeneral length and general width of a resonator.

FIG. 5B shows a shape 124 that results from a cut along the line 122 ofFIG. 5A. Such a shape is shown to include a boundary 126 that no longersupports a lateral wave along the major axis (of the original ellipse)and undergoing total reflections at the vertices (at the ends of themajor axis). Instead, a lateral wave (indicated as a single-ended arrow128) travelling along what is remaining of the major axis is shown topass through the remaining focus, and undergo a reflection at the angledboundary 126 so as to be directed away from the major axis.

In some embodiments, the example resonator shape of FIG. 5B can providea reduction in noise, when compared to the elliptical shaped resonatorof FIG. 3. However, and as shown in FIG. 5C, the shape 124 of FIG. 5Bstill includes a tangent surface 130 that can support a lateral wave(depicted as a double-ended arrow 134) between the tangent surface 130(at a location 132) and the surface associated with the boundary 126.

Accordingly, FIG. 5D shows that in some embodiments, another cut can bemade to the example shape 124 of FIGS. 5B and 5C. In FIG. 5D, such a cutcan be implemented along a line 136, and the resulting shape isindicated as 112 in FIG. 5E. FIG. 5D also shows an example of how alateral wave (depicted as a single-ended arrow 138) that would haveundergone reflections between the pair of planes 130, 126 in FIG. 5C, isnow directed away from the original direction (of the lateral wave 134of FIG. 5C).

It will be understood that in the example of FIG. 5D, other cuts can beimplemented to achieve a configuration of the cut line 136. For example,a cut can be made so that the reflected lateral wave (138 in FIG. 5D) isdirected to the left side of the original direction instead of to theright side (as in FIG. 5D). In some embodiments, the example cut of FIG.5D may be preferable since the reflected portion needs to travel furtherbefore encountering another boundary, and therefore being more likely tobe attenuated within the resonator.

In the example of FIG. 5E, the resonator 112 is shown to have lateralshape that includes curved boundaries 142, 144 that are parts of anelliptical shape, and straight boundaries 126, 140 that can be obtainedby respective cuts on the elliptical shape. In some embodiments, suchstraight boundaries may be easier to implement by cutting of anelliptical shaped resonator; however, it will be understood that aresonator having one or more features as described herein does notnecessarily require that any boundary have a curved shape or astraight-line shape. Accordingly, in the context of the ellipse-basedexample of FIG. 5E, each of the boundaries 126, 140 may or may not be astraight line.

FIGS. 6-10 show examples of comparison of performance parametersassociated with the example resonators of FIG. 2A (square shape), FIG.2B (circle shape), FIG. 3 (ellipse shape), and FIG. 5E (ellipse basedshaped with cuts). More particularly, FIG. 6 shows plots of scatteringparameter S21 for the square shaped resonator (FIG. 2A), the circleshaped resonator (FIG. 2B), and the ellipse shaped resonator (FIG. 3,with an aspect ratio of 2:1). FIG. 7 shows an enlarged view of theportion indicated as 150 in FIG. 6, for the square shaped resonator;FIG. 8 shows an enlarged view of the portion 150, for the circle shapedresonator; and FIG. 9 shows an enlarged view of the portion 150, for theellipse shaped resonator.

Referring to FIG. 7, one can see that in a region 152 of the enlargedview 150, the S21 fluctuates significantly, indicating that noise levelis relatively large for the square shaped resonator. Similarly, andreferring to FIG. 8, one can see that in a region 154 of the enlargedview 150, the S21 fluctuates significantly, indicating that noise levelis relatively large for the circle shaped resonator.

Referring to FIG. 9, one can see that in a region 156 of the enlargedview 150, noise level for the ellipse shaped resonator is noticeablysmaller than the noise levels for the square and circle shapedresonators. However, the noise level for the ellipse shaped resonator isstill significant.

FIG. 10 shows an enlarge region 150 similar to the examples of FIGS.7-9, but for a resonator having an ellipse based shape with cuts (112 inFIG. 5E). One can see that in a region 158 of the enlarged view 150,noise level for the ellipse based shape resonator 112 is significantlyreduced when compared to the ellipse shaped resonator example of FIG. 9.

In some embodiments, a shaped resonator having one or more features asdescribed herein can be implemented in a number of ways, including theexample described in reference to FIG. 5E. Such a shaped resonator canbe based on an elliptical shape, a non-elliptical shape, or anycombination thereof.

For example, in the context of ellipse-based resonators, FIGS. 11 and 12show resonators having one or more desirable features as describedherein. In a first example, FIG. 11A shows that in some embodiments, aresonator shape 112 of FIG. 11B can be achieved by combining twoellipse-based shapes 160, 162. More particularly, the firstellipse-based shape 160 can be obtained by cutting a portion of a fullellipse along a line parallel to its minor axis. Similarly, the secondellipse-based shape 162 can be obtained by cutting a portion of a fullellipse along a line parallel to its minor axis. In some embodiments,the first and second ellipse-based shapes 160, 162 can be identical. Insome embodiments, the first and second ellipse-based shapes 160, 162 maynot be identical.

Referring to FIG. 11A, the first and second ellipse-based shapes 160,162 can be arranged as shown (in which one is inverted with respect tothe other, and offset in X and Y directions), so as to result in anoverlapping region that includes overlapping boundaries 164, 166. Theoverall shape 112 of the resonator of FIG. 11B can be obtained bycutting or forming a resonator layer to include the outline of twoellipses, with boundaries associated with overlapping curves 164, 166.

Configured in the foregoing manner, lateral waves can be inhibited orreduced from being concentrated onto the major and minor axes associatedwith an ellipse. Accordingly, performance parameter such as noise can beimproved.

In a second example, FIG. 12A shows that in some embodiments, aresonator shape 112 of FIG. 12B can be achieved by combining two ellipseshapes 170, 172. More particularly, the first ellipse shape 170 can bearranged with the second ellipse shape 172, such that the major axes ofthe two ellipses are perpendicular. In some embodiments, such anarrangement can include a configuration where neither of the major andminor axes of each ellipse is fully included in the overlapping region,and none of the foci of the two ellipses coincide with another focus.

Referring to FIG. 12A, the first and second ellipse shapes 170, 172 canbe arranged as shown and described above, so as to result in anoverlapping region that includes overlapping boundaries 174, 176, 178,180. The overall shape 112 of the resonator of FIG. 12B can be obtainedby cutting or forming a resonator layer to include the such boundaries(174, 176, 178, 180).

Configured in the foregoing manner, lateral waves can be inhibited orreduced from being concentrated onto the major and minor axes associatedwith an ellipse. Accordingly, performance parameter such as noise can beimproved.

In the examples described above in reference to FIGS. 11 and 12, eachresonator shape 112 can be characterized by a polygon with a curvedsection joining a pair of vertices associated with each side of thepolygon. For example, FIG. 13A shows a resonator shape 112 that issimilar to the resonator shape 112 of FIG. 11B. Such a resonator shapeis shown to include four vertices that can be joined by four sides 184a, 184 b, 184 c, 184 d to define a four-sided polygon 182. The side 184a is shown to correspond to a curved section 186 a; the side 184 b isshown to correspond to a curved section 186 b; the side 184 c is shownto correspond to a curved section 186 c; and the side 184 d is shown tocorrespond to a curved section 186 d. It is noted that in the example ofFIG. 11B, each of the curved sections 186 a, 186 b, 186 c, 186 d is apart of an ellipse. However, it will be understood that in someembodiments, a curved section of a polygon-based resonator shape (e.g.,resonator shape 112 of FIG. 13A based on a four-sided polygon) can be aportion of an ellipse or a curved portion of a non-ellipse shape.

For example, FIG. 13B shows a resonator shape 112 that is similar to theresonator shape 112 of FIG. 12B. Such a resonator shape is shown toinclude four vertices that can be joined by four sides 184 a, 184 b, 184c, 184 d to define a four-sided polygon 182. The side 184 a is shown tocorrespond to a curved section 186 a; the side 184 b is shown tocorrespond to a curved section 186 b; the side 184 c is shown tocorrespond to a curved section 186 c; and the side 184 d is shown tocorrespond to a curved section 186 d. It is noted that in the example ofFIG. 12B, each of the curved sections 186 a, 186 b, 186 c, 186 d is apart of an ellipse. However, it will be understood that in someembodiments, a curved section of a polygon-based resonator shape (e.g.,resonator shape 112 of FIG. 13B based on a four-sided polygon) can be aportion of an ellipse or a curved portion of a non-ellipse shape.

In the examples of FIGS. 13A and 13B, each resonator shape 112 is basedon a respective four-sided polygon. In some embodiments, a resonatorshape can be based on a polygon having different number of sides. Forexample, FIG. 13C shows that in some embodiments, a resonator shape canbe based on a five-sided polygon 182 having five sides 184 a, 184 b, 184c, 184 d, 184 e. In another example, FIG. 13D shows that in someembodiments, a resonator shape can be based on a six-sided polygon 182having five sides 184 a, 184 b, 184 c, 184 d, 184 e, 184 f. Examplesrelated to the foregoing five-sided polygon 182 are described herein ingreater detail.

FIG. 14 shows an example of a resonator shape 112 that is based on afive-sided polygon 182 having five sides 184 a, 184 b, 184 c, 184 d, 184e. Such five sides are shown to be joined by five vertices havingindicated angles θ₁, θ₂, θ₃, θ₄, θ₅. More particularly, the vertex withthe angle θ₁ is between the sides 184 e and 184 a; the vertex with theangle θ₂ is between the sides 184 a and 184B; the vertex with the angleθ3 is between the sides 184 b and 184 c, the vertex with the angle θ4 isbetween the sides 184 c and 184 d; and the vertex with the angle θ5 isbetween the sides 184 d and 184 e.

In some embodiments, the angle θ1 can have a value of 108±10 degrees;the angle θ₂ can have a value of 105±10 degrees; the angle θ₃ can have avalue of 118±10 degrees; the angle θ4 can have a value of 105±10degrees; and the angle θ₅ can have a value of 104±10 degrees, such thatthe sum of the five angles is approximately 540 degrees. In someembodiments, the angle θ₁ can have a value of 108±5 degrees; the angleθ₂ can have a value of 105±5 degrees; the angle θ₃ can have a value of118±5 degrees; the angle θ₄ can have a value of 105±5 degrees; and theangle θ₅ can have a value of 104±5 degrees, such that the sum of thefive angles is approximately 540 degrees. In some embodiments, the angleθ₁ can have a value of 108±2 degrees; the angle θ₂ can have a value of105±2 degrees; the angle θ₃ can have a value of 118±2 degrees; the angleθ₄ can have a value of 105±2 degrees; and the angle θ₅ can have a valueof 104±2 degrees, such that the sum of the five angles is approximately540 degrees. In some embodiments, the angle θ₁ can have a value of 108±1degrees; the angle θ₂ can have a value of 105±1 degrees; the angle θ₃can have a value of 118±1 degrees; the angle θ₄ can have a value of105±1 degrees; and the angle θ₅ can have a value of 104±1 degrees, suchthat the sum of the five angles is approximately 540 degrees. In someembodiments, the angle θ₁ can have a value of approximately 108 degrees;the angle θ₂ can have a value of approximately 105 degrees; the angle θ₃can have a value of approximately 118 degrees; the angle θ₄ can have avalue of approximately 105 degrees; and the angle θ₅ can have a value ofapproximately 104 degrees, such that the sum of the five angles isapproximately 540 degrees.

In some embodiments, the angle θ₁ can have a value of 104±10 degrees;the angle θ₂ can have a value of 114±10 degrees; the angle θ₃ can have avalue of 116±10 degrees; the angle θ₄ can have a value of 102±10degrees; and the angle θ₅ can have a value of 104±10 degrees, such thatthe sum of the five angles is approximately 540 degrees. In someembodiments, the angle θ₁ can have a value of 104±5 degrees; the angleθ₂ can have a value of 114±5 degrees; the angle θ₃ can have a value of116±5 degrees; the angle θ₄ can have a value of 102±5 degrees; and theangle θ₅ can have a value of 104±5 degrees, such that the sum of thefive angles is approximately 540 degrees. In some embodiments, the angleθ₁ can have a value of 104±2 degrees; the angle θ₂ can have a value of114±2 degrees; the angle θ₃ can have a value of 116±2 degrees; the angleθ₄ can have a value of 102±2 degrees; and the angle θ₅ can have a valueof 104±2 degrees, such that the sum of the five angles is approximately540 degrees. In some embodiments, the angle θ₁ can have a value of 104±1degrees; the angle θ₂ can have a value of 114±1 degrees; the angle θ₃can have a value of 116±1 degrees; the angle θ₄ can have a value of102±1 degrees; and the angle θ₅ can have a value of 104±1 degrees, suchthat the sum of the five angles is approximately 540 degrees. In someembodiments, the angle θ₁ can have a value of approximately 104 degrees;the angle θ₂ can have a value of approximately 114 degrees; the angle θ₃can have a value of approximately 116 degrees; the angle θ₄ can have avalue of approximately 102 degrees; and the angle θ₅ can have a value ofapproximately 104 degrees, such that the sum of the five angles isapproximately 540 degrees.

In some embodiments, the angle θ₁ can have a value of 120±10 degrees;the angle θ₂ can have a value of 107±10 degrees; the angle θ₃ can have avalue of 101±10 degrees; the angle θ₄ can have a value of 126±10degrees; and the angle θ₅ can have a value of 86±10 degrees, such thatthe sum of the five angles is approximately 540 degrees. In someembodiments, the angle θ₁ can have a value of 120±5 degrees; the angleθ₂ can have a value of 107±5 degrees; the angle θ₃ can have a value of101±5 degrees; the angle θ₄ can have a value of 126±5 degrees; and theangle θ₅ can have a value of 86±5 degrees, such that the sum of the fiveangles is approximately 540 degrees. In some embodiments, the angle θ₁can have a value of 120±2 degrees; the angle θ₂ can have a value of107±2 degrees; the angle θ₃ can have a value of 101±2 degrees; the angleθ₄ can have a value of 126±2 degrees; and the angle θ₅ can have a valueof 86±2 degrees, such that the sum of the five angles is approximately540 degrees. In some embodiments, the angle θ₁ can have a value of 120±1degrees; the angle θ₂ can have a value of 107±1 degrees; the angle θ₃can have a value of 101±1 degrees; the angle θ₄ can have a value of126±1 degrees; and the angle θ₅ can have a value of 86±1 degrees, suchthat the sum of the five angles is approximately 540 degrees. In someembodiments, the angle θ₁ can have a value of approximately 120 degrees;the angle θ₂ can have a value of approximately 107 degrees; the angle θ₃can have a value of approximately 101 degrees; the angle θ₄ can have avalue of approximately 126 degrees; and the angle θ₅ can have a value ofapproximately 86 degrees, such that the sum of the five angles isapproximately 540 degrees.

It will be understood that other values or ranges of the five angles(θ₁, θ₂, θ₃, θ₄, θ₅) in FIG. 14 can be utilized. It will also beunderstood that dimensions of the five sides (184 a, 184 b, 184 c, 184d, 184 e) can be selected based on the overall lateral dimensions of theresonator, to support a given set of five angles, including the exampleangle sets described above.

In the example of FIG. 14, five curved sections corresponding to thefive sides 184 a, 184 b, 184 c, 184 d, 184 e are indicated as 186 a, 186b, 186 c, 186 d, 186 e, respectively. In some embodiments, each of suchcurved sections can be a curved section of an ellipse or a non-ellipseshape. For example, each of the curved sections 186 a, 186 b, 186 c, 186d, 186 e can be a portion of an ellipse.

In the context of the curved sections 186 a, 186 b, 186 c, 186 d, 186 ebeing parts of ellipses, it will be understood that in some embodiments,such curved sections can be parts of a plurality of ellipses. Forexample, a portion of a given ellipse can correspond to each curvedsection, such that the five curved sections 186 a, 186 b, 186 c, 186 d,186 e correspond to parts of five ellipses. In another example, a givenellipse can provide two curved sections (e.g., 186 e and 186 b), suchthat the five curved sections 186 a, 186 b, 186 c, 186 d, 186 ecorrespond to parts of less than five ellipses.

In some embodiments, a given curved section can be symmetric orasymmetric about a normal line at the midpoint of the correspondingside. In some embodiments, two neighboring curved sections (e.g., 186 eand 186 a) can be selected such that the two neighboring curved sectionsdefine an inward facing concave shape at the corresponding vertex (e.g.,at the vertex corresponding to angle θ₁).

FIG. 15 shows plots of scattering parameter S21 for various shapedresonators. Similar to the examples of FIGS. 6-10, larger fluctuationsin a given curve correspond to larger noise.

In FIG. 15, the S21 plot indicated as 190 a corresponds to a resonatorshape similar to the example of FIG. 5B; the S21 plot indicated as 190 bcorresponds to a resonator shape similar to the example of FIG. 5E; andthe S21 plot indicated as 190 c corresponds to a resonator shape similarto the example of FIG. 14. The S21 plot indicated as 190 d correspondsto a resonator shape having approximately half of a first ellipse withthe cut base having a concave shape of a second ellipse, such that theresonator shape is symmetric about the major axis fo the first ellipse.

Based on the examples shown in FIG. 15, one can see that the resonatorscorresponding to the plots 190 b (FIG. 5E) and 190 c (FIG. 14) providereduced noise when compared to the other configurations.

In the various examples described herein, a resonator shape can bedefined by an outline of an overlap of first and second electrodes of abulk acoustic resonator, where first electrode has a first lateral shapeand the second electrode has a second lateral shape. It will beunderstood that the first and second lateral shapes can have differentconfigurations to provide the resonator shape. For example, neither ofthe first and second lateral shape may have the same lateral shape asthe resonator shape, but when overlapped, the resulting outline can havethe resonator shape. In another example, at least one of the first andsecond lateral shape can be configured to have substantially the samelateral shape as the resonator shape. In such a configuration, one ofthe first and second lateral shape can be configured to havesubstantially the same lateral shape as the resonator shape, and theother lateral shape can be configured to have a larger area to therebyinclude a non-overlapping portion. Also in such a configuration, each ofthe first and second lateral shape can be configured to havesubstantially the same lateral shape as the resonator shape.

In some of the examples described herein, such as in the examples ofFIGS. 11-14, the foregoing resonator shape can include N curved sectionsjoined by N vertices of an N-sided polygon, where N can be, for example,an integer greater or equal to 4. For the purpose of description, itwill be understood that in some embodiments, each of such N curvedsections can be a smooth curve. Further, each of the N vertices can bedefined by joining of two neighboring smooth curves, such that the twoneighboring smooth curves combined is not a smooth curve due to therespective vertex. For example, and referring to the example of FIG. 14,each of the two neighboring curves 186 b and 186 c is a smooth curve,but the combination of the curves 186 b and 186 c with the vertextherebetween is not a smooth curve in embodiments when the two curvesare parts of separate shapes. Accordingly, in some embodiments, each ofthe N vertices can be a sharp point between two neighboring smoothcurves.

FIG. 16 shows that a FBAR device 100 having one or more features asdescribed herein can be implemented as, or be part of, a packaged filter200. In some embodiments, such a packaged filter can include a substrate202 on configured to support the FBAR functionality. In someembodiments, a FBAR device, such as the example of FIG. 4 (whichincludes its own substrate 102) can be mounted on another substrate(e.g., the packaging substrate 202 of FIG. 16). In some embodiments, thesubstrate 102 of the FBAR device 100 of FIG. 4 can also be the packagingsubstrate 202 of FIG. 16.

In some embodiments, the packaged filter 200 of FIG. 16 can beconfigured to provide radio-frequency (RF) operation.

FIG. 17 shows that an RF module 300 can include a FBAR device 100 havingone or more features as described herein. In some embodiments, such anRF module can include, a filter assembly 306, and one or more of theFBAR devices 100 can provide some or all filtering functionalities forsuch a filter assembly. In some embodiments, the RF module 300 can alsoinclude, for example, an RF integrated circuit (RFIC) 304, and anantenna switch module (ASM) 308. Such an example module can be, forexample, a front-end module configured to support wireless operations.

In some implementations, a device and/or a circuit having one or morefeatures described herein can be included in an RF device such as awireless device. Such a device and/or a circuit can be implementeddirectly in the wireless device, in a modular form as described herein,or in some combination thereof. In some embodiments, such a wirelessdevice can include, for example, a cellular phone, a smart-phone, ahand-held wireless device with or without phone functionality, awireless tablet, etc.

FIG. 18 depicts an example wireless device 400 having one or moreadvantageous features described herein. In the context of a modulehaving one or more features as described herein, such a module can begenerally depicted by a dashed box 300, and can be implemented as, forexample, a front-end module (FEM). In such an example, one or more FBARdevices as described herein can be included in, for example, an assemblyof filters such as duplexers 424.

Referring to FIG. 18, power amplifiers (PAs) 420 can receive theirrespective RF signals from a transceiver 410 that can be configured andoperated in known manners to generate RF signals to be amplified andtransmitted, and to process received signals. The transceiver 410 isshown to interact with a baseband sub-system 408 that is configured toprovide conversion between data and/or voice signals suitable for a userand RF signals suitable for the transceiver 410. The transceiver 410 canalso be in communication with a power management component 406 that isconfigured to manage power for the operation of the wireless device 400.Such power management can also control operations of the basebandsub-system 408 and the module 300.

The baseband sub-system 408 is shown to be connected to a user interface402 to facilitate various input and output of voice and/or data providedto and received from the user. The baseband sub-system 408 can also beconnected to a memory 404 that is configured to store data and/orinstructions to facilitate the operation of the wireless device, and/orto provide storage of information for the user.

In the example wireless device 400, outputs of the PAs 420 are shown tobe routed to their respective duplexers 424. Such amplified and filteredsignals can be routed to an antenna 416 through an antenna switch 414for transmission. In some embodiments, the duplexers 424 can allowtransmit and receive operations to be performed simultaneously using acommon antenna (e.g., 416). In FIG. 18, received signals are shown to berouted to “Rx” paths (not shown) that can include, for example, alow-noise amplifier (LNA).

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While some embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A bulk acoustic resonator comprising: apiezoelectric layer having a first side and a second side; and a firstelectrode having a first lateral shape implemented on the first side ofthe piezoelectric layer; and a second electrode having a second lateralshape implemented on the second side of the piezoelectric layer, thefirst and second lateral shapes selected and arranged to provide aresonator shape defined by an outline of an overlap of the first andsecond electrodes, the resonator shape including N smooth curves joinedby N vertices of an N-sided polygon having an inside, each vertexjoining two neighboring smooth curves such that the two neighboringsmooth curves combined is not a smooth curve due to the respectivevertex, each smooth curve having a concave shape with respect to theinside of the N-sided polygon, the resonator shape configured to have noaxis of symmetry.
 2. The bulk acoustic resonator of claim 1 wherein thequantity N of the number of vertices is an integer greater or equal to4.
 3. The bulk acoustic resonator of claim 2 wherein the quantity N ofthe number of vertices is equal to
 5. 4. The bulk acoustic resonator ofclaim 1 wherein each of the N vertices is a sharp point between therespective neighboring smooth curves.
 5. The bulk acoustic resonator ofclaim 1 wherein each of the N smooth curves is a part of an ellipse. 6.The bulk acoustic resonator of claim 5 wherein at least two of the Nsmooth curves are parts of one ellipse.
 7. The bulk acoustic resonatorof claim 5 wherein the N smooth curves are parts of N respectiveellipses.
 8. The bulk acoustic resonator of claim 1 wherein the bulkacoustic resonator is a film bulk acoustic resonator.
 9. The bulkacoustic resonator of claim 1 wherein neither of the first and secondlateral shape has the same lateral shape as the resonator shape.
 10. Thebulk acoustic resonator of claim 1 wherein at least one of the first andsecond lateral shape is configured to have substantially the samelateral shape as the resonator shape.
 11. The bulk acoustic resonator ofclaim 10 wherein one of the first and second lateral shape is configuredto have substantially the same lateral shape as the resonator shape, andthe other lateral shape is configured to have a larger area to therebyinclude a non-overlapping portion.
 12. The bulk acoustic resonator ofclaim 10 wherein each of the first and second lateral shape isconfigured to have substantially the same lateral shape as the resonatorshape.
 13. A film bulk acoustic resonator device comprising: asubstrate; first and second electrodes implemented over the substrate;and a piezoelectric layer implemented between the first and secondelectrodes that are configured to provide a resonator shape defined byan outline of an overlap of the first and second electrodes, theresonator shape including N smooth curves joined by N vertices of anN-sided polygon having an inside, each vertex joining two neighboringsmooth curves such that the two neighboring smooth curves combined isnot a smooth curve due to the respective vertex, each smooth curvehaving a concave shape with respect to the inside of the N-sidedpolygon, the resonator shape configured to have no axis of symmetry. 14.The film bulk acoustic resonator device of claim 13 wherein the filmbulk acoustic resonator device is a radio-frequency filter.
 15. Apackaged module comprising: a packaging substrate configured to receivea plurality of components; and a film bulk acoustic resonator deviceimplemented on the packaging substrate, the film bulk acoustic resonatordevice including a substrate, and first and second electrodesimplemented over the substrate, the film bulk acoustic resonator devicefurther including a piezoelectric layer implemented between the firstand second electrodes that are configured to provide a resonator shapedefined by an outline of an overlap of the first and second electrodes,the resonator shape including N smooth curves joined by N vertices of anN-sided polygon having an inside, each vertex joining two neighboringsmooth curves such that the two neighboring smooth curves combined isnot a smooth curve due to the respective vertex, each smooth curvehaving a concave shape with respect to the inside of the N-sidedpolygon, the resonator shape configured to have no axis of symmetry. 16.The packaged module of claim 15 wherein the packaged module is afront-end module configured to support wireless operations involvingradio-frequency signals.
 17. The packaged module of claim 16 wherein thefront-end module is configured to provide cellular communicationfunctionality.